Analytical models for machine tool motion behavior assessment bench mark subjected to great earthquake

Abstract

Three large earthquakes hit japan in the last few years continuously. It affected country's economy and hard to recover specially the manufacturing sector. For avoiding such impacts in the future, lessons were studied and actions were taken. This study therefore was conducted to assess the basic minimum machine tool motion behavior criteria by utilizing the existing seismic data. Particularly, the japan real earthquake data (The 2004 chūetsu and the great hanshin earthquakes as well as the 2011 Tūhoku earthquake) and mathematical models that mimic the movement of machine tools with screw jack mounting during seismic occurrence were considered and developed. For the validity, both mathematical analysis and experimental performances of a previously developed small mock-up structure of a machine tool were conducted. The study concludes that (1) the possible motion behavior of a machine tool was able to be defined and calculated; (2) using the existing real seismic data able to predict the motion behaviour of a machine tool; and (3) it was observed that up-to approximately 60 % accuracy obtained when using the real earthquake data and the developed mathematical models for analysing machine tool motion behavior.

Risk Management Regrading Crashing or Falling Down of Several Machine Tools in a Machine Shop at a Large Earthquake

“…The results of this research are summarized as follows; (1) Three physical computational models in the previous research [9] were used to calculate the parallel, rotational and falling down behavior of a machine tool during an earthquake. (2) Based on the data of three earthquakes, the Great Hanshin-Awaji Earthquake, the Great Chuetsu Earthquake and the Great East Japan Earthquake, a physical earthquake model was developed, and a risk management method for the crash and the falling down of machine tools in the machine shop during a large earthquake was proposed.…”

“…2, Table 3), the parallel and rotational behaviours in the physical earthquake model (Fig. 1, Table 2) in Chapter 2 are calculated by the physical calculation models in the previous research [9]. The results of this calculation are only an example of how the machine tool structure shown in Fig.…”

“…All the 3) during the physical earthquake (Table 2). These movable areas were calculated for countermeasure of the crashing between several machine tools by the physical calculation models in the previous research [9]. This method was used for risk management of the machine tools during a large earthquake.…”

“…Safety measures to prevent machine tools from falling down during an earthquake are discussed. The possibility of the machine tool falling down during an earthquake can be calculated using the physical calculation model in the previous research [9] for the falling down behaviour during the physical earthquake model (Figure 1, Table 2) in Chapter 2, using the machine tool structure (Figure 2, Table 3) described above. By simply changing the values of the representative variables in Tables 2 and 3, it is easy to take measures to prevent the tipping over of machine tool structures of different sizes and specifications.…”

“…Thus, the height of the centre of gravity of the machine tool may change during actual machining. Therefore, as a risk management measure to prevent the machine tool from falling down, it is essential to check that the machine tool will not tip over even at the height of the machine tool centre of gravity when the maximum workpiece weight in the machine tool specifications is raised to the maximum height, using a physical calculation model in the previous research [9] and a physical earthquake model (Table 2). The safety factor can then be ensured by changing the data of the physical earthquake model to the less dangerous one.…”